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FarmerJoeVT 
Silver Level
Joined: 19 Oct 2014
Location: Vermont
Points: 58
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 Topic: AC 715B - Boom won't retract and is leaking hydro
Posted: 19 Oct 2014 at 7:33pm |
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Hi,
We recently purchased a used AC 715-b backhoe and loader. Unfortunately the only thing we didn't have test before purchasing is now cause us the biggest problems. We brought it home and after extending the boom, it would only retract slightly almost like it is unable to move. When I looked at it, the nipple at the bottom of the backhoe arm slightly above the digger has a steady flow of hydraulic fluid. Has anyone ever had this issue or have any suggestions on how to fix it?
Any advice or guidance is greatly appreciated.
Very respectfully,
Brian
VT
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Coke-in-MN
Orange Level Access
Joined: 12 Sep 2009
Location: Afton MN
Points: 41567
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Posted: 19 Oct 2014 at 7:49pm |
THere are fittings on cylinders that ARE welded and it might be cracked at weld the cylinders on the stabilizers on my machine had cracks at end of cylinder tubes from people raising them to fast and slamming the internal piston rod into end of cylinder . When you say the digger ? or is this a extenda hoe or ? One cylinder in inside the dipper , one external on same , one for the bucket mounted on the boom . Leak at the gland at shaft means bad seal , internal leakage means bad seals on piston or bad piston. Gland has 2 sets of seals one to tube and one to rod - gland is held in by threaded collar . System has a regenerative circuit where oil from one end of piston is transferred to opposite side as cylinder moves - this speeds up movement of hoe .
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
Points: 81041
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Posted: 19 Oct 2014 at 8:17pm |
here is a basic drawing of a cylinder. Where does it leak ?
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Like them all, but love the "B"s.
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Calvin Schmidt
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Joined: 11 Sep 2009
Location: Ontario Can.
Points: 4525
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Posted: 20 Oct 2014 at 5:11am |
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If it has been leaking like you say, check the oil level in the tank first. Will still have to repair the leak.
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Nothing is impossible if it is properly financed
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Dave A
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Joined: 11 Sep 2009
Location: Almond Wisconsi
Points: 855
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Posted: 20 Oct 2014 at 2:34pm |
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does it make any noise when you try to move the boom. If it goes one way but not the other chances the ram is still good. You will have to check the pressures on the system 2350 on part of the system 3000 on the other. Spool alignment is very important on the regen system
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Play the game for more than you can afford to lose... only then will you learn the game.
Winston Churchill
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Steve in NJ
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Joined: 12 Sep 2009
Location: Andover, NJ
Points: 11788
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Posted: 24 Oct 2014 at 7:58am |
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As Cal mentioned, the first thing you check is hydro level. If the thing has been leaking pretty good, it won't take to long to lower the level in the hydraulic tank to where function is affected...
Steve@B&B
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39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife
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FarmerJoeVT
Silver Level
Joined: 19 Oct 2014
Location: Vermont
Points: 58
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Posted: 03 Nov 2014 at 3:47pm |
Problem found: turns out that the boom
extension plate was missing. So when I extended the boom out it didn’t know
when to stop. When it extended all the way out the weight of the are hinged on
the cylinder and bent it with the piston not allowing it to extend back in.
Does anyone know where to get a replacement one? In the interim, I removed the
damaged cylinder/piston for the boom function and slid the arm back up and
locked it in place with a tractor hitch pin. Now it basically operates as a
basic backhoe minus the extension boom.
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